Development and demonstration of a non-invasive and clinically practical device for quantifying resistance to passive motion in patients with muscle spasticity is proposed herein. Spasticity is a disabling consequence of disease or injury to the central nervous system and/or muscle, such as traumatic brain injury, stroke, tumor, cerebral palsy, spinal cord injury, or multiple sclerosis. Spasticity can lead to severe restrictions in physical activity and participation in society, motor incoordination, muscle tightness and bony deformities, and spasm- related pain. The proposed device will provide a reliable, valid, fast, and relatively inexpensive means to quantify and analyze spasticity in subjects' limbs, provide measurement/analysis results to healthcare practitioners, and store measurements for future use, such as for evaluation of therapy and treatment effectiveness. This device will emulate aspects of the Ashworth Scale for spasticity, which grades resistance felt by an examiner during passive movement using an ordinal scale. However, new device will provide important new information by: (1) quantifying the absolute magnitude of spasticity (rather than a mere ordinal ranking); (2) calculating the rate of change in resistance; (3) evaluating the velocity-dependency of the response; and (4) differentiating spasticity from stiffness and voluntary/other involuntary muscle activation through use of electromyogram (EMG) recordings. PROPOSED COMMERCIAL APPLICATIONS: Diagnostic precision, and ultimately treatment prescription and outcomes, will be enhanced by the proposed device, which will have considerable economic impact in healthcare. This device addresses deficiencies in treatment protocols currently based on clinical impressions rather than definitive evidence of the presence and degree of spasticity. This device will facilitate optimal treatment choices and outcomes for the millions of patients who have motor disabilities characterized by spasticity.